Question

我有一个使用游标运行SQlite查询的应用程序。

    public Cursor totaltrips(){
    Cursor cursor = database.rawQuery("SELECT * AS TTotal FROM " + DatabaseHelper.TABLE_NAME, null);
    return cursor;
}

结果存储在最多5个值的Arraylist中。如果数据库中没有记录，则应用程序崩溃。如果我有一个或多个数据库条目，它工作正常。有没有人知道如何在没有数据库条目时阻止它崩溃？

 // get column value
    if (Distance.moveToNext())
        result = String.valueOf(Distance.getDouble(Distance.getColumnIndex("myTotal")));

    tnmView.setText(result);

    List<String> distancearray = new ArrayList<String>();
    Cursor cursor =  dbManager.totaldistance();


    do{
        distancearray.add(cursor.getString(1));
    }while ((cursor.moveToNext()));
    ttrips = cursor.getCount();
    Log.i("Graph", "TTRIPS = " + ttrips);

    // Be sure here to have at least the 5 desired elements into the list
    while(distancearray.size() < 5){
        distancearray.add("0");
    }

应用程序因错误而崩溃

android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0

在线

do{
        distancearray.add(cursor.getString(1));
    }while ((cursor.moveToNext()));

Answer 1

检查光标是否确实有结果，尝试类似这样的事情：

int numResults = cursor.getCount();
if (numResults > 0) {
    do {
        distancearray.add(cursor.getString(1));
    } while ((cursor.moveToNext()));
}

Answer 2

替换

do{
    distancearray.add(cursor.getString(1));
}while ((cursor.moveToNext()));

与

if (cursor != null) {
    while (cursor.moveToNext()) {
        distancearray.add(cursor.getString(1));
    }
    cursor.close();
}

Answer 3

检查游标是否为空且具有多个值。使用后关闭游标。

public MainWindow() {
    xpsViewer.AddHandler(Hyperlink.RequestNavigateEvent, new RequestNavigateEventHandler(OnRequestNavigate));
}

private void OnRequestNavigate(object sender, RequestNavigateEventArgs e) {
    // URI contains the page number (e.Uri = "...#PG_7_LNK_2")
    int pageNumber;
    if (int.TryParse(Regex.Match(e.Uri.ToString(), @"(?<=PG_)[0-9]+").Value, out pageNumber)) {
        xpsViewer.GoToPage(pageNumber);
    }
}

如果SQLite游标没有结果，应用程序崩溃

3 个答案: